Thermite method of abandoning a well

ABSTRACT

A method of conveying materials or tools into a well, the well including a plurality of lengths of concentric tubing, comprising the step of permitting at least one cartridge to free-fall under gravity into the well. No line may be connected to the cartridge. The cartridge is selected from a group of cartridges which may comprise, a cartridge including thermite, hermetically sealed from well fluids, a cartridge including low temperature alloy, hermetically sealed from well fluids, a cartridge formed from low temperature alloy, a cartridge including a detonator triggered by impact, a cartridge including a detonator triggered by an electronic or mechanical clock, a cartridge formed from tungsten carbide, a bridge plug cartridge including slips to retain the bridge plug in a position against the wall of well tubing, a thermal barrier material, or a shock absorber that absorbs energy from subsequent cartridges being dropped.

Over the past 20 years or so a large number of offshore structures havebeen constructed which are now or will soon be exhausted and will needto be abandoned. These offshore structures may comprise productionplatforms which are either steel or concrete structures resting on thesea bed or floating platforms. Numerous conduits are connected to theseoffshore structures to carry the various fluids being gas, oil or wateretc., which are necessary for the production of oil and/or gas from thewell.

In abandoning a well, consideration has to be given to the potentialenvironmental threat from the abandoned well for many years in thefuture.

In the case of offshore structure there is usually no rig derrick inplace which can be used to perform the required well abandonmentprocedure. Therefore it is typically necessary to install a new derrickor alternatively a mobile derrick can be positioned above the well. Thisrequirement adds considerable expense to the task of abandoning theoffshore well, compared to a land based well.

A typical production well will comprise a number of tubular conduitsarranged concentrically with respect to each. The method of abandoningthe well which is presently known in the art involves the separatesealing of each of the concentric conduits which requires a large numberof sequential steps.

In the abandonment method known in the art the first step is to seal thefirst central conduit usually by means of cement or other suitablesealant. The first annular channel between the first and second conduitsis then sealed and the first central conduit is then cut above the sealand the cut section is removed from the well.

The second annular channel between the second and third conduits is thensealed and the second conduit cut above the seal and the cut section isremoved from the well.

This process is repeated until all the conduits are removed. The numberof separate steps required is typically very large indeed and the numberof separate operations is five times the number of conduits to beremoved. This adds considerably to the cost of the well abandonment dueto the time taken and the resources required at the well head.

It is the purpose of the present invention to provide a method ofabandoning a well which avoids the disadvantageous and numerousoperations which are required by the existing known methods. This willgreatly reduce the costs of safely abandoning a well. It is a furtherobjective of the invention to provide a method of abandoning a wellwithout the requirement of a rig which involves significant expenseparticularly in subsea based wells.

It is a further advantage of the invention to isolate all the conduitsand annuli with no return of the well bore tubulars to the surface.Furthermore, the method of abandonment of the well will comply with allthe regulatory guidelines for the isolation of a well.

According to the present invention there is provided a method ofabandoning a well, by connecting a set of cartridges together by aconnection means and either dropping them into a well or lowering themon a cable into a well. The cartridges could consist of an ignitor, alow temperature thermite, a high temperature thermite, low temperaturealloys (bismuth), bridge plug, thermal barrier to protect the bridgeplug, shock absorber.

According to another aspect of the present invention to install thecartridges using a highly automated means of deploying into a subseawell

According to another aspect of the invention, once the subsea apparatusis connected to the well, it has sufficient materials (cartridges), plugremoval and storage tool, cartridge lowering means to perform all taskswithout having to be disconnected from the well.

According to a further aspect of the invention significant tubing isconsumed to expose a large length of the next casing outside it. Theoperation above can be repeated until the open hole formation isexposed.

According to a further aspect of the invention, while the thermite andsurround formation is still hot and above the natural formationtemperature, a low melting point alloy can be distributed within thethermite, this alloy has a very low viscosity and flows into any crack,void or fissure. During cool down all the fissures and conductivepassages are plugged by the then cooled down to ambient temperaturesolidified metal alloy. Thus the well is plugged well out into thenatural rock formation away from the well in multiple zones and wellboreitself is permanently plugged by a magma mass.

According to a further aspect of the invention the sealing materialcould be a two part resin deployed cartridges by gravity.

According to a further aspect of the invention, the sealing materialcould comprise a low melting point alloy deployed using gravity andmelted in situ using an electric heating element.

According to a further aspect of the invention, a cartridge with superreactive thermite could be used to cut the tubing or casing at apre-defined place in the well.

According to a further aspect of the invention, a cartridge with bauxitecould combine with the thermite and fuse resulting in additional sealingcapability.

According to a further aspect of the invention, retarded thermite couldheat the tubing or casing to a temperature below its melting point. Thiswill result in the tubing or casing losing its mechanical strength, butnot melting it.

According to a further aspect of the invention, the ignitor could bedeployed as a cartridge.

According to a further aspect of the invention the thermite is used tosever the riser pipe the required distance below the mud line (typical10-20 ft)

According to a further aspect of the invention ceramic balls aredeposited on top of the thermite to contain the thermite and increaseits temperature and direct the thermite energy to part the tubing orcasing.

According to a further aspect of the invention tungsten carbide ballscould be deposited on top of the thermite

According to a further aspect of the invention a ceramic barrier with adeflector surface on it to contain the thermite energy and direct it topart the tubing.

According to a further aspect of the invention many tools can bedeployed and docked together downhole to form a long assembly.

According to a further aspect of the invention, the ceramic balls ortungsten carbide balls could be dropped from surface to form a heavybarrier onto of the thermite.

Thus by means of the method according to the invention the number ofoperations required is greatly reduced, thus resulting in a considerablereduction in the cost of carrying out the well abandonment.

The following is a more detailed description of an embodiment accordingto the invention by reference to the following drawings in which:

FIG. 1 is an illustration of a section side view through a well withvarious cartridges deposited inside the tubing lining the well;

FIG. 2 is a similar view to FIG. 1, after the different materials in thecartridges have reacted and have returned to the stable wellboretemperature;

FIG. 3 is section side view through a well with a casing and productiontubing, with different cartridges installed inside the productiontubing;

FIG. 4 is a similar view to FIG. 3, showing a subsequent stage in theprocess;

FIG. 5 is a similar view to FIG. 4, showing a subsequent stage in theprocess;

FIG. 6 is a similar view to FIG. 5, showing a subsequent stage in theprocess;

FIG. 7 is a similar view to FIG. 6, showing a subsequent stage in theprocess;

FIG. 8 is a similar view to FIG. 7, showing a subsequent stage in theprocess;

FIG. 9 is a section side view through a cartridge with features a topand bottom to enable the rapid assembly or more than one cartridge toanother;

FIG. 10 is a section side view through a cartridge with a male andfemale thread top and bottom;

FIG. 11 is a section side view through a cartridge with a male andfemale mating features and a cross hole for a dowel pin to locksubsequent cartridges together;

FIG. 12 is a section side view through a cartridge with a timer,battery, electric circuitry, and a solid state ignitor material to setoff the thermite reaction;

FIG. 13 is a section side view through a cartridge with a shock absorberbuilt into it;

FIG. 14 is a section side view through a cartridge with low temperaturepellets stored inside it;

FIG. 15 is a section side view through a cartridge which is machinedfrom low temperature alloy;

FIG. 16 is a section side view through a cartridge with a pressuresensitive switch, which enables slips to be energised and set thecartridge at a controlled depth in the well;

FIG. 17 is a similar view to FIG. 16, with the slips activated;

FIG. 18 is a section side view of a subsea wellhead, Christmas tree andvarious workover packages installed on top of it to enable thecartridges to be deployed into the well in a controlled way;

FIG. 19 is a similar view to FIG. 18 at a different stage of theoperation;

FIG. 20 is a similar view to FIG. 19 at a different stage of theoperation;

FIG. 21 is a similar view to FIG. 20 at a different stage of theoperation;

FIG. 22 is a section side view of a platform wellhead, Christmas treeand a workover package installed to enable cartridges to be installed inthe well in a controlled way;

FIG. 23 is a section side view of an apparatus to rapidly supplycartridges to drop them into the well;

FIG. 24 is a section side view of a platform with an apparatus to enablethe rapid positioning of a slickline lubricator over any of the wellswithout the use of a crane;

FIG. 25 is a similar view to FIG. 24 with the lubricator connected to awellhead;

FIG. 26 is a similar view to FIG. 24 with the lubricator orientatedhorizontally to enable a tool to be loaded or unloaded;

FIG. 27 is a plan view of a platform work deck with the equipmentpreviously described performing multiple concurrent operations;

FIG. 28 is a section side view of a well, with a bridge plug installedand a crumple type shock absorber dropped onto of it;

FIG. 29 is a similar view to FIG. 28 with a cartridge dropped on top ofthe shock absorber;

FIG. 30 is a similar view to FIG. 29 with the crumple shock absorberabsorbing the impact from the cartridge above it and protecting thebridge plug below it;

FIG. 31 is a side view of a cartridge designed to separate the tubingoutside it;

FIG. 32 is a section plan view XX of FIG. 31;

FIG. 33 is a section side view of FIG. 31;

FIG. 34 is a section side view of another embodiment of the cartridge;

FIG. 35 is a section side view through a tubing string in a well withanother embodiment of tubing separating using thermite, a ceramic ortungsten directing face and ceramic or tungsten carbide balls;

FIG. 36 is a section side view through a well with the resulting partedtubing by the tool operation in FIG. 35;

FIG. 37 is a subsequent operation to FIG. 36 in which and ignitor andthermite cartridges are deposited through the tubing and they land ontop of the ceramic or tungsten carbide balls and additional balls aredeposited onto of the thermite;

FIG. 38 is a subsequent operation to FIG. 37 with the thermite ignitedand the ceramic or tungsten carbide balls act like a stop and cause thecasing to be severed;

FIG. 39. A,B,C,D,E Is a section side view through a different versionsof a cartridge;

FIG. 40 is a section side view through an ignitor type cartridge; and

FIG. 41 A,B Is a section side view through second embodiment of aignitor type cartridge;

FIG. 42 A, B, C is a sections side view through a slickline or wirelinedeployed and ignitor, the ignitor being activated by a mass or furthercartridges being dropped on top of it;

FIG. 43 is a section side view of the wellhead deck, and the upper deck,with a BOP attached to the well and an automated cartridge loadingsystem, loading cartridges into the well.

Referring to FIGS. 1 and 2 our cartridge method of deployment wouldenable us to deploy different combinations and quantities of thedifferent materials. We could for example deploy normal thermite 1 if wewanted to melt the casing, or retarded thermite (not shown) if we didnot want to melt the casing, we could deploy distributed ignitors 2, asa back up or to ignite at different depths in different sequence, and wecould distribute the low temperature alloy 3, so when the thermite magnacools, it forms a solid magna in the borehole 4 with a small amount ofslag 5 on top of it, any cracks or fissures 6 or small leak paths in theadjacent formation will still have low viscosity low melting point alloy7 free to fill these which when cooled down to the formation temperatureset hard and provide multiple seals 8 deep into the formation along theopen hole. This combination of materials can enable any length of openhole seal to be achieved, without removing any of the tubing, casing orother equipment in the well.

Referring to FIGS. 3 to 8, an objective of this process is to get anaccess window to the open hole. How we achieve this is as follows; Thecartridge assembly, consisting of a bridge plug 10, thermal barrier 11,ignitors 12, low temperature or retarded thermite 13, high temperaturethermite 14, a running tool 15 and either slickline 16 or electricwireline used to lower the assembly into the well.

The running tool could contain electronics to initiate the setting ofthe bridge plug 10 and ignitors 12, or the bridge plug and ignitorscould have internal timers to initiate their operation after a setperiod of time. The bridge would first have to set, and be pull testedby the slickline tool to ensure it had set correctly. The slickline toolcould then be disconnected and returned to surface, or at least a safedistance above the top of the assembly. The lower ignitor 12 wouldignite the low temperature thermite, this will react up to about 1250 C,this is below the melting point of the steel of the tubing it is inside,but it is sufficiently hot, and sufficient mass to make the whole glowred and loss all its mechanical strength, the upper ignitor 17 willignite the high temperature thermite, this will reach 3000 C and willresult in parting the adjacent tubing 18, and because the well is nearvertical, gravity and the mass of the tubing and thermite will result init collapsing against the internal diameter of the casing 19 outside it.This will result in a window 20 of significant length exposing the ID ofthe casing 19. As a rule of thumb, if we put inside the tubing 600 ft ofcartridges we would create a window of about 300 ft. Clearly thisdepends on the tubing wt. its diameter relative to the ID of the casing19. The tubing steel and thermite will form a solid metal magma mass,with a quantity of slag 21 on top. Now additional cartridges 22 can beeither lowered into the well or dropped from surface to repeat theoperation on the next casing 19 outside.

Referring to FIGS. 9 to 17 there are shown various embodiments of thecartridge, FIG. 9 shows a thin wall tube 220 with a lower end 221 bondedto the ID of the lower end of the thin wall tube 220, a circular wall222 enclosing the lower end. A collet feature 23 extends from theenclosing surface 222. At the upper end, is top cap 24 which is bonded25 into the ID of the tube 20. It has a closed in circular wall 26 whichhermetically seals the contents of the tube. The contents 27 could bethermite, bauxite, or other material. The upper cap includes a recess 28where it can be gripped by automated handling equipment, with thecontents providing additional rigidity. An upper opening 29 allows thecollet 23 of another cartridge to dock with this cartridge and a recess30 allows the collet to permanently engage and lock the cartridgestogether, requiring no orientation.

An alternative method of connecting the cartridges would be have a male31 and female 32 course thread incorporated into the end fittings 33,34respectively. These would include a recess 35 for a handling system toengage, and a circular double-sided shoulder 36,37 with a shoulder angleof 27.5 degrees on each side. These act as a torque shoulder and preventthe threads from unscrewing.

Another alternative is to a simple male pin 40 and female hole 41, witha cross drilled hole 42 in which would be driven a dowel pin (not shown)this would need to be orientated to achieve this.

The lowest most cartridge could include a bull nose 50 this could be aseparate part to be attached to a string of cartridges, or it could beintegral with the end cap if the cartridge was to be dropped into thewell on an individual basis.

Referring to FIG. 12, the cartridge could also contain a battery poweredelectronic timer ignitor. This would ignite a mixture 60 of bariumperoxide and aluminium powder in a weight ratio of about 15:4. This is astable mixture and can ignite at a relatively low temperature.

The electronic timer would be in a hermetically sealed unit 61 in thecap 62. It would consist of a battery 63, which cannot be active until arip cord 64 is pulled. Once this is pulled the circuit is complete, andan LED 65 provides positive indication it is active. An electronic timer66 counts a set amount of time (1 hr to 4 hrs typically) Once the timehas elapsed, the circuit over heats the resistor 67 which initiates theignition mixture 60, which then sets of the thermite 68.

Referring to FIG. 13, if the cartridges are dropped into the well usinggravity, when they would come to rest on a bridge plug, the impact couldsufficient especially when repeated many times be dropping many of thesecartridges (100's meters potentially) they could unset the slips whichhold the bridge plug to the tubing ID. By fitting a shock absorbercartridge (described below) between the bridge plug the thermite orignitor cartridge the impact forces seen by the bridge plug slips willbe significantly reduced. The shock absorber is quite simple, itsprinciple parts consist of a cylinder 70 with a reduced ID 71 whichtraps a piston 72 of a long mandrel 73 of the moving part of theassembly. A spring 74 inside the cylinder keeps the tool fully extended,when a cartridge impacts the upper end 75 of the tool wellbore fluidinside the chamber has to exit through the narrow gap between the piston72 and the cylinder wall 70, on the return stroke, wellbore fluid caneasily enter the chamber 76 via a passage 77 and check valve 78.

Referring to FIGS. 14 and 15, the inside of the cartridge could befilled with low temperature alloy bismuth, in the form of small pellets80 or the entire cartridge could be machined from bismuth 81. Thebismuth would be heated by the thermite reaction, and it becomesextremely low viscosity, and remains very liquid as the thermite coolsdown, the benefit of combining this material is it fills any cracks orfissures that are created by the thermite reaction.

Referring to FIGS. 16 and 17, a cartridge module could be aelectronically activated bridge plug, this could be time delayed, orpressure activated, so that slickline operations can be eliminated andthe bridge plug can be dropped into the well and be activated at therequired depth, there would be some degree of inaccuracy in its exactplacement but it would eliminate the slickline operation completely. Orit could be deployed with a complete cartridge assembly as described inFIGS. 1 and 2. So a single slickline run could deploy the completecartridge assembly. The bridge plug cartridge would consist of astandard upper and lower connection in this case 31, 32. Slips 90 wouldbe retained in the unset position by pins 91, the pressure activatedsensor 92, when at the pre-set hydrostatic pressure will release a cord93 which allows the piston 94 move downwards into a chamber 95 with onlyatmospheric pressure in it. As the piston moves, the tapped pins 91 arenaturally pushed inwards 96 allowing the spring 97 to push the slipsupwards and push them up on the tapered surface 98 pushing the teeth 99of the slips into the production tubing.

Referring to FIGS. 18 to 21 there is shown an apparatus which can beattached to a subsea well to access the well and deploy a string ofcartridges into the well to perform the function as discussed earlier.

There is shown a subsea wellhead 100, connected to it is a subseahorizontal Christmas tree 101, to access the well a crown plug 102 hasto be removed. The well workover package consists of an adaptor 103which connects to the top of the tree.

The work over package consists of the following;

a tree plug removal and park tool 104,

a well control package 105

a slickline and lubricator package 106

a cartridge store and automatic loader package 107

From the top of the assembly, a rod 110 is extended from the plugstorage area 111, it latches into the plug 102, unsets it and retractstogether with the plug back into the plug garage 111. This is thenrotated 180 degrees on its base 112, so that it is out of the way andthe slickline lubricator 113 is aligned over the wellbore. Access to thewell is now possible.

An automated cartridge deployment system can load the cartridges to bedeployed in the well in a sequential manner. Cartridges are stored in alarge storage container 114, are feed into the main bore 115 and grippedby a travelling gripper 116, this holds onto a cartridge 117 and latchesit into a cartridge below it already in the well 118. Once connectionconfirmed, static grippers 119 release from cartridge 120, the assemblycan be lowered down one cartridge and the static gripper can grip ontocartridge 118. Once this is confirmed, the travelling gripper 116 canrelease from cartridge 117 and then repeat the operation. This can berepeated until the required number and type of cartridges have beeninstalled 121. The slickline tool 122, can then be lowered and latchedinto the upper receptacle 123 of the upper cartridge 124. The connectionis first tested, and then the static gripper 119 on 125 can be releasedand the assembly can be run into the well with full control.

Once at the required setting depth the slickline can set the bridge plugand release from the top cartridge. It can return to surface and theprocess can be repeated to deploy another set of cartridges.

Referring to FIGS. 22 and 23 there is shown a platform wellhead,Christmas tree 131, well control package 132 and a loading mechanism133. Cartridges are stored in hoppers 134, 135, a gate 136, 137 isopened to allow the controlled feed of cartridges onto a conveyor 138.The conveyor can be moved in the horizontal direction 139 so that itwill be over the wellhead being serviced. Once the cartridge arrives atthe wellhead it can be selectively picked up, orientated vertically 140and dropped into a rotating barrel feeder 141. The rotating barrelfeeder can access a pressurised well to drop the cartridge into thewell, or an automated feeder described in FIGS. 18 to 21 to latch thecartridges together and deploy them using slickline can be positionedover the wellhead. The line feed hoppers 134, 135 can be topped up inreal time with top up hoppers 142, 143.

Referring to FIGS. 24 to 26 the slickline lubricators 150 will bemounted in a swivel 151 which can orientate them from the vertical 152to horizontal 153 for tool string loading and service.

The arm 154 holding the lubricators is mounted to a pillar 155 which canjacked up and down 156, rotated 157 and traversed 158 along a rail 159so it can access any one of the 20 wells 160 on the platform shown.

Once in position the crane is no longer required for lubricatorconnection and disconnection from the BOP, this will significantlyimprove well operations.

Referring to FIG. 27 shows a plan view of all the equipment required,and it shows the philosophy of a factory abandonment process, that isconcurrent operations, i.e. 3 wells can be in different sequence ofabandonment

Well 1 Slickline operation 170

Well 5 Pressure test 171

Well 9 Thermite cartridges deposited in it 172

Referring to FIGS. 28 to 30. There is shown a bridge plug 180 describedearlier in FIGS. 16, 17 set in the tubing 181. A shock absorber 182 isdropped from surface to protect the bridge plug from the subsequentcartridges 190 to be dropped. As the first cartridge hits the top 183 ofthe shock absorber, the end of the shock absorber flares open 185because of the slits 184, this flaring open cascades down the shockabsorber, as each recess 186, 187 are natural fold lines and the slits188 readily collapse. As the folds expand they contact the ID of thetubing 189 and this prevents further collapse, preventing any seriousforces being applied to the bridge plug, so any number of cartridges canbe dropped and the bridge plug will be isolated from the impact loads.

Referring to FIGS. 31 to 38 there is shown a cartridge with a hightemperature housing 200 and base 201, inside the housing is hightemperature thermite 202, the base has a profile 203 which directs theignited thermite out of ports 204, the ports 204 are filled with a lowtemperature material such as bismuth or plastic to keep the thermiteisolated from the wellbore fluids. When the thermite exits the port ithits the ID tubing 205 and cuts through it. Above the thermite arecartridges of ceramic or tungsten carbide balls, these provide both aweight and sealing effect to contain the thermite and ensure the maximumheat and force is located at the pipe serving jet.

An alternative arrangement could be a plug 210 which has a ceramic ortungsten carbide deflector 211, and ceramic or tungsten carbide pistonrings 212, these contain the thermite reaction 213 and direct the energyto sever the tubing 214, in addition the plug could have a set of oneway slips 215 which prevent the plug being displaced up the tubing, butallow the free movement down of the plug. Above the plug could beadditional weight provided by cartridges of ceramic or tungsten carbideballs 216.

Once the tubing is severed, the remaining tubing, thermite and ceramicballs form a plug 220 and a window or access 221 to the next casing outis available. More thermite cartridges 222 and ignitor 223 can bedeposited into the space 221 via the tubing 224, then either cartridgesof tungsten carbide balls can be deposited on top 225 of the thermite,or they can be poured into the well from surface, as small and heavy andwill fall on top 225 of the thermite inside the larger casing diameter221 and form a seal and weight ensure the thermite can get to atemperature and energy sufficient to sever the casing 226. This casingwill then drop and form a plug with the thermite and tungsten carbideballs.

If another casing is outside this one (not shown) this operation can berepeated, until access to the cap rock is achieved. Once access to thecap rock is achieved bismuth can be deposited on top of the hot mass andit will melt and seal all cracks and fissures. Then when the thermitecools down to formation temperature the bismuth will go solid and expandby up to 3% to provide a permanent abandonment seal to the well.

Referring to FIGS. 39 to 44 there is shown a slickline tool assembly toachieve the same goal. It would be installed into the well in severalruns, so any desired length of thermite can be deployed. Typically inwell operations, tool strings of about 30 ft are only possible, in thisexample we have 5 separate runs into the well, so this assembly could bein the order of (5×30 ft) 150 ft.

Referring particularly to FIG. 42, the first module consists of apressure set anchor, known pressure is applied and the check valve 340moves a sleeve 341 downwards, this activates two slips 342, 343, thislock the anchor to the tubing, and the seal 344 provides a mechanicalbarrier. Above the seal is a thermal barrier 345 this is a ceramic orsilica flour or sand material to protect the anchor from the heatgenerated by the thermite 346 above. At the very top of the tool is astandard GS running profile 347, in which a standard slickline tool canengage and disengage.

The next tool has a collet 348 to dock into the profile 347. This tooljust contains thermite 349, and any number of these can be run dependinghow long a thermite plug is desired.

The next tool is similar to the previous tool, but with the addition ofa mechanically operated ignitor. It has a slightly modified upperprofile 350, which works in combination with the lower profile of thenext tool 351. When 350 and 351 are connected, the collet 352 locatesinto the profile 353, a second collet 354 connects to the profile 355,now these rods are permanently connected, finally, a tool with tungstencarbide balls is connected to provide a seal and weight. This could alsobe like to deflector 310.

To activate the ignitors, the tool string is extended, the collet 352can travel longitudinally in the recess 353, the rods 354, 355 movewhich breaks the seals 360, 361, on one side of the seal is glycerine362, 363, and on the other is potassium permanganate 364, 365 andmagnesium ribbon 366, 367. This we have two ignitors for the thermite.

At the top of the chamber 370 is a deflector 371 and ports 372 and itfunction has been described earlier.

Referring to FIGS. 39 to 41, there is shown a cartridge assembly 301,which is either a hollow container which could be made from plastic,aluminium, low temperature alloy, or a solid billet 302 of lowtemperature alloy as shown in E. It could be a made from a continuoustube 303, with bottom 304 and top 305 ends, the ends could be shapedwith a male point 306 at the bottom and a corresponding femalereceptacle 307 at the top, this would allow them to stack together, andhelp guide the cartridge into the well without hanging up on any edges.

The inside of the tube could be filled with regular thermite, which canburn at up to 2,500° C., or be a retarded thermite powder 308 which willburn at around 1,000-1,250° C. when ignited. This powder consists of amixture of aluminium, iron oxide and silica sand present in the ratiosof 25:75:44. The silica sand acts as a moderator has an 100-200 meshparticle size and the iron oxide is dry roasted and has an oxygencontent of approximately 16% to 18% by weight

The inside of the tube could also be filled with pellets of lowtemperature alloy 309

The end could be attached via friction welding, glue 310, or threads 311

The cartridge could also contain an ignitor, this could consist of achamber 312 filled with KMnO4. A glass barrier 313, hermitically sealingthis upper chamber. A small lower chamber 314 below the glass barriercontaining glycerine. A pin 315 positioned to fracture the glassbarrier. A shear pin 316 prevents the pin 315 from moving untilsufficient weight of cartridges is above it. A further shipping safetypin 317 is added, additional safety.

The cartridge could also contain a battery powered electronic timerignitor. This would ignite a mixture 320 of barium peroxide andaluminium powder in a weight ratio of about 15:4. This is a stablemixture and can ignite at a relatively low temperature.

The electronic timer would be in a hermetically sealed unit 321 in thecap 322. It would consist of a battery 323, which cannot be active untila rip cord 324 is pulled. Once this is pulled the circuit is complete,and an LED 325 provides positive indication it is active. An electronictimer 326 counts a set amount of time (1 hr to 4 hrs typically) Once thetime has elapsed, the circuit over heats the resistor 327 whichinitiates the ignition mixture 320.

Referring to FIGS. 42 A, B, C, D, a slickline ignitor tool consists oftwo sections;

The upper section, this consists of the following. A GS running profile331, A chamber 332 filled with KMnO4. A glass barrier 333, hermiticallysealing this chamber. A small chamber 334 above the glass barriercontaining glycerine. A pin 335 positioned to fracture the glassbarrier.

The lower section, this consists of the following;

A length of blank pipe 336 to space out the slips 337 away from theignitor reaction, inside the blank pipe is sand 338 or other thermalbarrier material. A slip arrangement 337 to set the tool inside thetubing at any desired depth. A cup seal 339 to provide a pressurebarrier, and a check valve 340 to allow well fluid pass the cup sealwhile installing or lowering the tool in the well.

A heavy weight 341 could be dropped from surface and its tip 341′ wouldland on the pin 335, resulting in it cracking the glass and initiatingthe ignitor.

Alternatively, the upper housing 342, could be held in an extendedposition by shear pins 343, when the weight of sufficient cartridgesabove it are present, it will shear the pins and again initiate theignitor. Each cartridge will weigh about 7 lbs so, possibly we could setthe shear pin value to be 500 lbs, so we would need in excess of 72cartridges above it to shear the pins.

Referring now to FIG. 43, there is shown a wellhead housing 360 andChristmas tree 361 on top of which is attached a blow out preventer(BOP) 362, then a short extension tube 363 from the top of the BOP tothe upper deck 364. The cartridges previously described would be loadedinto containers 365, these would be mounted on a skid 366. Inside thecontainers they would be arranged on their side and on a sloping lowersurface 367 so they would flow out of an open exit passage 368 freelyunder gravity. On exit, each cartridge would be oriented vertically andbe conveyed on a conveyor to the upper entrance of the tube 363, theconveying belts 369 grip the cartridges and provide positive placementalong the belt. At the end above the tube 363 the belts are positivelydisengaged from the cartridge 370 so the cartridge can free fall intothe tube 363. Many containers can be linked together. The conveyorsystem 380, can be stored out of the way for transport, and can bepositioned over any well by a combination of telescopically extending it381, moving it axially 382 and adjusting its height over the well 383.

1. A method of conveying materials or tools into a well, the wellincluding a plurality of lengths of concentric tubing, comprising thesteps: permitting at least one cartridge to free-fall under gravity intothe well.
 2. The method according to claim 1, wherein no line isconnected to the cartridge.
 3. The method according to claim 1, whereinthe cartridge is selected from a group of cartridges which may comprise:a cartridge including thermite, hermetically sealed from well fluids; acartridge including low temperature alloy, hermetically sealed from wellfluids; a cartridge formed from low temperature alloy; a cartridgeincluding a detonator triggered by impact; a cartridge including adetonator triggered by an electronic or mechanical clock; a cartridgeformed from tungsten carbide; a bridge plug cartridge including slips toretain the bridge plug in a position against the wall of well tubing; athermal barrier material; and a shock absorber that absorbs energy fromsubsequent cartridges being dropped.
 4. The method according to claim 1,wherein the cartridges are automatically fed into the top of the well.5. A cartridge for use in a well, adapted to be allowed to free fallunder gravity through the well, wherein the cartridge comprises ahousing hermetically sealed from well fluids.
 6. The cartridge accordingto claim 5, wherein the cartridge houses either thermite, a lowtemperature alloy, or a heat-shielding material.
 7. The cartridgeaccording to claim 5 wherein for the bottom of the cartridge beingpointed.
 8. The cartridge according to claim 7, wherein the top of thecartridge has a concave shape corresponding to the pointed bottom end.9. The cartridge according to claim 5 further comprising a bridge plugwhich includes slips which are capable of being activated to retain thebridge plug in a position against the wall of well tubing.
 10. Thecartridge according to claim 5 further comprising a collapsible sectionwhich absorbs shock from items which fall on top of the cartridge. 11.The cartridge according to claim 5 further comprising which includes adetonator capable of triggering a thermite reaction.
 12. The cartridgeaccording to claim 11, wherein the cartridge includes an electronic ormechanical clock to trigger the detonator.
 13. The cartridge accordingto claim 11, wherein the detonator is triggered by the action of thecartridge being brought to a halt in the well after being allowed tofree fall down the well.
 14. The cartridge according to claim 11,wherein the detonator is triggered by the action of another cartridgebeing dropped on it from above.
 15. A cartridge for use in a well,formed predominantly of low temperature alloy or of tungsten carbide.